Phase II study of oral S-1 with irinotecan and bevacizumab (SIRB) as first-line therapy for patients with metastatic colorectal cancer

Dexamethasone to prednisolone rotation relieved hiccups in colorectal cancer patient continuing teleworking during anticancer therapy

We present a case of chemotherapy-induced hiccups that were alleviated by steroid rotation. Hiccups are often overlooked, but they have an impact on the patient's quality of life. In the COVID-19 era, web-based teleworking has become an important tool, hiccups during a teleconference should be noted as a concern for patients.

Evaluation of the Expression Profile of Irinotecan-Induced Diarrhea in Patients with Colorectal Cancer

Irinotecan (CPT-11) is widely used for the treatment of unresectable colorectal cancer in combination with fluoropyrimidines, such as 5-fluorouracil and S-1. Diarrhea is one of the adverse effects associated with CPT-11 and frequently reported by patients treated with CPT-11-containing regimens combined with oral fluoropyrimidines. However, the mechanisms involved in this process, as well as whether fluctuations in the frequency and differences in the onset time of diarrhea with each CPT-11-containing regimen are caused by drug interactions remain unclear. Therefore, we examined the incidence of diarrhea caused by each CPT-11-containing regimen in patients with colorectal cancer using data from the large voluntary reporting Japanese Adverse Drug Event Report (JADER) database. Firstly, we searched for suspected drugs related to the occurrence of diarrhea using reported odds ratio and calculated the signal score to assess drug–drug interactions. Subsequently, we conducted a time-to-onset analysis using Weibull distribution. The results showed that the combination of CPT-11 with S-1 increased the frequency of diarrhea due to a pharmacological interaction but delayed its onset. The present results may contribute to the appropriate management of drug-induced adverse effects by healthcare professionals.

A phase I/II study of S-1 and irinotecan (IRIS) combined with cetuximab in patients with RAS wild-type metastatic colorectal cancer (KSCC1401)

PURPOSE

This study was designed to assess the tolerability, efficacy, and safety of tri-weekly irinotecan plus S-1 (IRIS) and weekly cetuximab in patients with metastatic colorectal cancer (mCRC).

METHODS

The main eligibility criteria were RAS wild-type mCRC with no prior chemotherapy. S-1 was given orally at a dose of 40 mg/m² (40-60 mg) twice for 2 weeks, followed by a 1-week rest. Irinotecan was given on day 1 of each cycle at a dose of 150 mg/m². Cetuximab was administered on days 1 (400 mg/m²), 8 (250 mg/m²), and 15 (250 mg/m²), and then once weekly (250 mg/m²) thereafter. A standard 3 + 3 phase I dose de-escalation design was used to determine the maximum tolerated dose and the recommended dose (RD) of irinotecan. The primary end point of the Phase II study was overall response rate (ORR).

RESULTS

Between December 2014 and September 2017, 4 and 54 patients were enrolled in phase I and phase II studies, respectively. No dose-limiting toxicity was observed in the phase I study, and the RD of irinotecan was 150 mg/m². In the phase II study, the ORR was 56.9% (90% confidence interval 44.4%-68.7%). The safety profile revealed that the most common grade 3/4 adverse events were neutropenia (31.4%), appetite loss (27.5%), hypokalemia (11.8%), and diarrhea (11.8%). Grade 3/4 hand-foot skin syndrome occurred in nine patients (9.8%).

CONCLUSION

This study showed that the efficacy and safety of IRIS combined with cetuximab were comparable to those for other first-line treatments. This regimen is a good candidate for first-line treatment of RAS wild-type mCRC.

S-1 and CPT-11 Plus Ramucirumab (IRIS+Rmab) as Second-Line Chemotherapy for Patients with Oxaliplatin-Refractory Metastatic Colorectal Cancer (mCRC): A Multicenter Phase II Study in Japan (N-DOCC-F-C-1701)

This multicenter phase II N-DOCC-F-C-1701 trial is being planned in order to investigate the efficacy and safety of CPT-11+S-1 +Ramucirumab (IRIS+Rmab), which is anticipated to have a stronger anti-tumor effect than IRIS+Bmab in patients with metastatic colorectal cancer (mCRC) previously treated with oxaliplatin (L-OHP) containing regimen, in consideration of the result of RAISE, FIRIS and some phase II trials of IRIS+Bevacicizumab (Bmab). The number of patients is set at 38 for the statistical analysis, assuming an expected median PFS of 5.0 months (threshold: 3.0 months). The primary endpoint of the study is the progression free survival (PFS), and the secondary endpoints are the overall response rate (ORR), overall survival (OS), adverse events (AE), quality of life (QOL) and review of nausea and vomiting. This trial is registered in the UMIN Clinical Trials Registry as UMIN000028170. We intend to start conducting the trial in September 1, 2017. If this trial meets the endpoint, IRIS+Rmab might be supported as a new optional standard regimen for mCRC.

Oral S-1 with 24-h Infusion of Irinotecan plus Bevacizumab versus FOLFIRI plus Bevacizumab as First-Line Chemotherapy for Metastatic Colorectal Cancer: An Open-Label Randomized Phase II Trial

BACKGROUND

FOLFIRI plus bevacizumab have been widely used as first-line treatment for metastatic colorectal cancer (mCRC). Pharmacokinetics and pharmacodynamics suggested a low dose of irinotecan given as a long-term infusion is expected to enhance antitumor activity. We conducted a randomized phase II study to compare oral S-1 with a 24-h infusion of irinotecan plus bevacizumab versus FOLFIRI plus bevacizumab.

METHODS

The subjects comprised 120 chemotherapy-naïve patients with mCRC. The study group received a 24-h infusion of irinotecan at a dose of 125 mg/m2 on days 1 and 15, combined with oral S-1 80 mg/m2 on days 1-14 (24h-SIRI/B). The FOLFIRI/B group received irinotecan at a dose of 150 mg/m2, 5-fluorouracil given at a dose of 400 mg/m2 as a bolus injection and at a dose of 2,400 mg/m2 as a 46-h infusion, and 200 mg/m2 leucovorin on days 1 and 15. Bevacizumab was given at a dose of 5.0 mg/kg on days 1 and 15 in both groups. Treatment was repeated every 4 weeks. The primary endpoint was 1-year progression-free survival (PFS). Secondary endpoints were PFS, response rates (RR), overall survival (OS), and adverse events (AEs).

RESULTS

From December 2013 through January 2018, 120 patients were randomly assigned, 61 patients to the 24h-SIRI/B and 59 patients to the FOLFIRI/B. The median follow-up period was 22.8 months. The 1-year PFS rate was 43.14% in the 24h-SIRI/B arm and 19.15% in the FOLFIRI/B arm (HR = 0.312 [95%CI 0.13-0.78], p = 0.01). The median PFS was 10.2 months (95%CI 8.8-14.3) and 10.0 months (95%CI 7.4-11.0), and the median OS was 29.7 months (95%CI 22.9-43.9) and 28.8 months (95%CI 18.4-ND), respectively (p = 0.3758, p = 0.8234). The overall RR was 86.3 and 61.7%, respectively (p = 0.0053). AEs were similar.

CONCLUSIONS

Our results show that the 24h-SIRI/B regimen is an effective and reasonably well-tolerated regimen for the first-line treatment of mCRC.

S-1 and irinotecan plus bevacizumab versus mFOLFOX6 or CapeOX plus bevacizumab as first-line treatment in patients with metastatic colorectal cancer (TRICOLORE): a randomized, open-label, phase III, noninferiority trial

Background

Combination therapy with oral fluoropyrimidine and irinotecan has not yet been established as first-line treatment of metastatic colorectal cancer (mCRC). We carried out a randomized, open-label, phase III trial to determine whether S-1 and irinotecan plus bevacizumab is noninferior to mFOLFOX6 or CapeOX plus bevacizumab in terms of progression-free survival (PFS).

Patients and methods

Patients from 53 institutions who had previously untreated mCRC were randomly assigned (1 : 1) to receive either mFOLFOX6 or CapeOX plus bevacizumab (control group) or S-1 and irinotecan plus bevacizumab (experimental group; a 3-week regimen: intravenous infusions of irinotecan 150 mg/m2 and bevacizumab 7.5 mg/kg on day 1, oral S-1 80 mg/m2 twice daily for 2 weeks, followed by a 1-week rest; or a 4-week regimen: irinotecan 100 mg/m2 and bevacizumab 5 mg/kg on days 1 and 15, S-1 80 mg/m2 twice daily for 2 weeks, followed by a 2-week rest). The primary end point was PFS. The noninferiority margin was 1.25; noninferiority would be established if the upper limit of the 95% confidence interval (CI) for the hazard ratio (HR) of the control group versus the experimental group was less than this margin.

Result

Between June 2012 and September 2014, 487 patients underwent randomization. Two hundred and forty-three patients assigned to the control group and 241 assigned to the experimental group were included in the primary analysis. Median PFS was 10.8 months (95% CI 9.6-11.6) in the control group and 14.0 months (95% CI 12.4-15.5) in the experimental group (HR 0.84, 95% CI 0.70-1.02; P < 0.0001 for noninferiority, P = 0.0815 for superiority). One hundred and fifty-seven patients (64.9%) in the control group and 140 (58.6%) in the experimental group had adverse events of grade 3 or higher.

Conclusion

S-1 and irinotecan plus bevacizumab is noninferior to mFOLFOX6 or CapeOX plus bevacizumab with respect to PFS as first-line treatment of mCRC and could be a new standard treatment.

Clinical trials number

UMIN000007834.

A phase II study of bevacizumab and irinotecan plus alternate-day S-1 as a second-line therapy in patients with metastatic colorectal cancer: the AIRS study

BACKGROUND

The aim of this single-arm phase II clinical trial was to evaluate whether the alternate-day administration of S-1 plus irinotecan would reduce the incidence of severe diarrhea in comparison to consecutive-day S-1 administration (standard IRIS regimen) in second-line treatment for patients with metastatic colorectal cancer.

METHODS

Patients with metastatic colorectal cancer after failure with first-line treatment of oxaliplatin and fluoropyrimidine were enrolled. Irinotecan (150 mg/m²) and bevacizumab (5 mg/kg) were given intravenously on day 1. Oral S-1 was administered on alternate days at a dose of 40-60 mg twice a day. Cycles were repeated every 2 weeks. The primary endpoint was the incidence of grade ≥ 3 diarrhea. Our hypothesis set 21% as a threshold incidence and 10% as an expected incidence from previous studies with one-sided alpha 0.05. The secondary endpoints included the relative dose intensity, progression-free survival, overall survival and other adverse events.

RESULTS

A total of 51 patients were enrolled. The incidence of grade ≥ 3 diarrhea was 15.7% (8/51). Other common grade ≥ 3 adverse events were neutropenia, anemia, thrombocytopenia and fatigue were 13.7% (7/51), 5.9% (3/51), 2.0% (1/51) and 5.9% (3/51), respectively. The relative dose intensities of irinotecan, bevacizumab, and S-1 were 80.0, 86.8, and 77.7%, respectively. The median progression-free survival and overall survival were 8.4 months (5.8-9.8) and 17.1 months (11.8-22.3).

CONCLUSIONS

The alternate-day S-1 administration does not have significant effectiveness to reduce diarrhea in patients who received second-line treatment for metastatic colorectal cancer.

Difference in Neutropenia due to Administration Schedule of TAS-102

TAS-102 significantly improves overall survival in patients with metastatic colorectal cancer. The most common adverse event of TAS-102 is bone marrow suppression, which leads to neutropenia. The incidence of neutropenia is high, and there is no known effective prevention method. Furthermore, the administration method of TAS-102 is complicated. We reported that neutropenia could be avoided by changing to a simple administration method of TAS-102.

Study protocol of the TRICOLORE trial: a randomized phase III study of oxaliplatin-based chemotherapy versus combination chemotherapy with S-1, irinotecan, and bevacizumab as first-line therapy for metastatic colorectal cancer

Background

Metastatic colorectal cancer carries a poor prognosis and cannot be cured by currently available therapy. Chemotherapy designed to prolong survival and improve the quality of life (QOL) of patients is the mainstay of treatment. Standard regimens of FOLFOX/bevacizumab and CapeOX/bevacizumab can cause neurotoxicity, potentially disrupting treatment. The results of 3 phase II studies of combination therapy with S-1, irinotecan, and bevacizumab showed comparable efficacy to mFOLFOX6/bevacizumab and CapeOX/bevacizumab, without severe neurotoxicity. Therefore, the establishment and evaluation of S-1-containing irinotecan-based regimens for first-line treatment are expected to become more important.

Methods

The TRICOLORE trial is a multicenter, randomized, open-label, controlled phase III study which aims to evaluate the non-inferiority of combination therapy with S-1/irinotecan/bevacizumab (a 3-week regimen [SIRB] or 4-week regimen [IRIS/bevacizumab]) to oxaliplatin-based standard treatment (mFOLFOX6/bevacizumab or CapeOX/bevacizumab) in patients with metastatic colorectal cancer who had not previously received chemotherapy. Patients will be randomly assigned to either the control group (mFOLFOX6/bevacizumab or CapeOX/bevacizumab) or study group (SIRB or IRIS/bevacizumab). The target sample size is 450 patients. The primary endpoint is progression-free survival (PFS), and the secondary endpoints are overall survival (OS), response rate (RR), time to treatment failure (TTF), relative dose intensity (RDI), the incidence and severity of adverse events, quality of life (QOL), quality-adjusted life years (QALY), health care costs, and relations between biomarkers and treatment response (translational research, TR).

Discussion

The results of this study will provide important information that will help to improve the therapeutic strategy for metastatic colorectal cancer, and we believe that this study is very meaningful from the perspective of comparative effectiveness research.

Trial registration

UMIN000007834

Electronic supplementary material

The online version of this article (doi:10.1186/s12885-015-1630-1) contains supplementary material, which is available to authorized users.

Systemic therapy for colorectal cancer: patterns of chemotherapy and biologic therapy use in nationally representative US claims database

BACKGROUND

Treatment strategies for colorectal cancer (CRC) are highly variable. The aim of this study is to examine the patterns of chemotherapy and biologic therapy use for CRC patients in a national medical claims database.

METHODS

A retrospective and observational analysis was performed using the i3 Innovus claims database to identify healthcare services consumed by patients aged 18 years and older, diagnosed with CRC between 1 January 2005 and 30 June 2009 in commercial health plans.

RESULTS

Of 9,876 subjects diagnosed with CRC, fluorouracil (23.5 %) and capecitabine (10.0 %) were the dominant first-line monotherapies, followed by bevacizumab (3.2 %) and oxaliplatin (2.9 %). The most common combination regimen at first line and first and second line was FOLFOX (fluorouracil, leucovorin, and oxaliplatin; more than 25 %). The combinations FOLFIRI (fluorouracil, leucovorin, and irinotecan) plus bevacizumab (14.2 %) and FOLFOX plus bevacizumab (13.9 %) were significantly more frequent in third and successive lines of CRC therapy than other regimens (χ(2) = 191.2; P < 0.01). Additionally, the average annualized cost of CRC treatment for all patients was $US66,452, and the adjusted analysis demonstrated that patients receiving FOLFOX-A (FOLFOX + avastin) or FOLFIRI-A (FOLFIRI + avastin) had higher costs for CRC treatment.

CONCLUSIONS

With the exception of a sizeable portion of patients on monotherapy, the treatment patterns for CRC were largely consistent with National Comprehensive Cancer Network (NCCN) guidelines.

The SOFT trial: a Phase III study of the dihydropyrimidine dehydrogenase inhibitory fluoropyrimidine S-1 and oxaliplatin (SOX) plus bevacizumab as first-line chemotherapy for metastatic colorectal cancer

ABSTRACT 

A combination of oxaliplatin, leucovorin and 5-fluorouracil (FOLFOX) plus bevacizumab has been widely used for the first-line chemotherapy of metastatic colorectal cancer (mCRC). S-1 is an oral fluoropyrimidine preparation that combines tegafur, a prodrug of 5-fluorouracil, with two modulators. Several studies of combination chemotherapy with oxaliplatin plus S-1 (SOX) conducted in Asia have reported promising efficacy and safety in patients with mCRC, suggesting the potential to replace mFOLFOX6. The SOFT trial (JapicCTI-090699) was a randomized Phase III trial designed to evaluate the noninferiority of SOX plus bevacizumab to mFOLFOX6 plus bevacizumab in patients with mCRC. This review summarizes the drug concept of S-1 and the results of clinical trials of S-1 and SOX in CRC and presents an overview of the SOFT trial.

A Phase II Trial of Combined Chemotherapy with Oral S-1 and 24-Hour Infusions of Irinotecan plus Bevacizumab in Patients with Metastatic Colorectal Cancer

OBJECTIVES

Protracted low-dose infusion of irinotecan has been suggested to enhance antitumor activity. A phase II study was conducted to evaluate the safety and efficacy of oral S-1 combined with 24-hour infusion of irinotecan and intravenous bevacizumab for metastatic colorectal cancer (MCRC).

METHODS

The subjects were 79 patients with MCRC; 57 were chemotherapy naïve. Irinotecan (125 mg/m(2)) was administered as a 24-hour infusion on days 1 and 15, S-1 (80 mg/m(2)) was administered orally on days 1-14, and bevacizumab (5.0 mg/kg) was given on days 1 and 15. The treatment was repeated every 4 weeks.

RESULTS

Median follow-up was 20.0 months, and the mean number of cycles was 7. The overall response rate was 79.7% (95% CI, 69.2-88.0), 86.0% (95% CI, 74.2-93.7) for first-line and 63.6% (95% CI, 40.7-82.8) for second-line treatment. The median progression-free survival was 16.4 months (95% CI, 13.9-21.0) for first-line and 9.4 months (95% CI, 4.9-16.5) for second-line treatment. The median overall survival was not reached. Grade 3-4 toxicities were neutropenia (43%), leukopenia (20.3%), anorexia (19.0%), and diarrhea (10.1%). Toxicity was tolerable.

CONCLUSIONS

Combination chemotherapy with oral S-1 and biweekly 24-hour infusions of irinotecan plus bevacizumab appears to be highly active and well tolerated both as first-line and second-line chemotherapy for MCRC.

Efficacy of S-1 in colorectal cancer

INTRODUCTION

S-1 is an oral fluoropyrimidine that consists of tegafur, 5-chloro-2, 4-dihydroxypyridine and potassium oxonate. It has been developed as a prodrug of 5-fluorouracil with the goal of improving therapeutic efficacy and tolerability.

AREAS COVERED

This review aims to provide an evidence-based update of clinical trials that have investigated the clinical efficacy, adverse-event profile, dosage and administration of S-1, given alone or in combination with conventional chemotherapeutics and new target-oriented drugs, in the management of colorectal cancer (CRC). Additionally, differences in the tolerability and pharmacokinetics of S-1 between Caucasians and Asians have been described. Finally, the therapeutic efficacy of S-1 regarding metastatic CRC or postoperative CRC has been discussed. Available data have stimulated further research, including Phase III trials for the treatment of advanced CRC.

EXPERT OPINION

Treatment using S-1 combined with oxaliplatin (± bevacizumab) and irinotecan has achieved promising results in terms of feasibility, safety and effectiveness. Furthermore, S-1 is an acceptable treatment as adjuvant chemotherapy for colon cancer.

Complete response of lung metastases from rectal cancer to combination first-line therapy of S-1 and irinotecan plus bevacizumab: A case report and review of the literature

This report presents the case of a 72-year-old male who had undergone abdominoperineal resection following a diagnosis of lower rectal cancer with multiple lung metastases. Pathologically, the resected specimen exhibited advanced rectal cancer with regional lymphoid metastases and was classified as stage IV disease. S-1 and irinotecan (IRIS) plus bevacizumab combination therapy was used to treat the lung metastases following the surgery. S-1 (100 mg/body) was administered orally on days 1–14 of a 28-day cycle, and irinotecan (125 mg/m²) and bevacizumab (7.5 mg/kg) were administered by intravenous infusion on days 1 and 15. Computed tomography revealed a marked decrease in the size of the metastases following three therapeutic courses, and no lung metastases or new lesions were detected following nine therapeutic courses. The response was declared clinically complete. The patient refused additional treatment following nine therapeutic courses, and there was no recurrence 36 months after the final course of therapy. This case demonstrates the efficacy of IRIS plus bevacizumab as a first-line combination therapy against lung metastases of rectal cancer.

Phase II study of oral S-1 plus cisplatin with bevacizumab for advanced non-squamous non-small cell lung cancer

BACKGROUND

We conducted a phase II study to evaluate the efficacy and safety of S-1 plus cisplatin with bevacizumab followed by maintenance bevacizumab in patients with advanced non-squamous non-small cell lung cancer (NSCLC).

PATIENTS AND METHODS

Chemotherapy-naïve patients received S-1 plus cisplatin with bevacizumab. S-1 (80 mg/m(2)) was administered orally twice daily for 14 days, cisplatin (60 mg/m(2)) on day 1, and bevacizumab (15 mg/kg) on day 1 and every 3 weeks for 4-6 cycles. Patients with an objective response or stable disease received maintenance bevacizumab every 3 weeks until disease progression.

RESULTS

Thirty patients were enrolled in this study. The median number of chemotherapy was four (range, 1-6 cycles), and the median number of bevacizumab alone was three (range, 1-31 cycles). The grade 3/4 toxicities were neutropaenia (23%), thrombocytopaenia (10%), febrile neutropaenia (3%), hypertension (17%), pneumonia (7%), and bowel perforation (3%). The objective response rate was 71% (95% CI, 55-88%) for a disease control rate of 100%. The median progression-free and overall survival times were 7.0 months and 20.0 months, respectively.

CONCLUSIONS

S-1 plus cisplatin with bevacizumab is an active and well-tolerated regimen in patients with chemotherapy-naïve non-squamous NSCLC.

Synthesis and in vitro evaluation of [18F]BMS-754807: a potential PET ligand for IGF-1R

Radiosynthesis and in vitro evaluation of [(18)F](S)-1-(4-((5-cyclopropyl-1H-pyrazol-3-yl)amino)pyrrolo[2,1-f][1,2,4]triazin-2-yl)-N-(6-fluoropyridin-3-yl)-2-methylpyrrolidine-2-carboxamide ([(18)F]BMS-754807 or [(18)F]1) a specific IGF-1R inhibitor was performed. [(18)F]1 demonstrated specific binding in vitro to human cancer tissues. Synthesis of reference standard 1 and corresponding bromo derivative (1a), the precursor for radiolabeling were achieved from 2,4-dichloropyrrolo[2,1-f][1,2,4]triazine (4) in three steps with 50% overall yield. The radioproduct was obtained in 8% yield by reacting 1a with [(18)F]TBAF in DMSO at 170°C at high radiochemical purity and specific activity (1-2Ci/μmol, N=10). The proof of concept of IGF-IR imaging with [(18)F]1 was demonstrated by in vitro autoradiography studies using pathologically identified surgically removed grade IV glioblastoma, breast cancer and pancreatic tumor tissues. These studies indicate that [(18)F]1 can be a potential PET tracer for monitoring IGF-1R.

Development and characterization of a reliable mouse model of colorectal cancer metastasis to the liver

Colorectal cancer (CRC) is the third most frequent cancer and the third leading cause of cancer deaths in the United States (American Cancer Society, Cancer facts and figures 2012, 20121). The major cause of death is metastasis and frequently, the target organ is the liver. Successful metastasis depends on acquired properties in cancer cells that promote invasion and migration, and on multiple interactions between tumors and host-derived cells in the microenvironment. These processes, however, occur asymptomatically, thus, metastasis remains poorly understood and often diagnosed only at the final stage. To facilitate the elucidation of the mechanisms underlying these processes and to identify the molecular regulators, particularly at the early stages, we developed a mouse model of hepatic metastasis of CRC by cecal implantation of a mouse adenocarcinoma cell line in an immune competent host that reliably recapitulates all steps of tumor growth and metastasis within a defined period. By in vivo selection, we isolated cells of varying metastatic potential. The most highly metastatic CT26-FL3 cells produced liver metastasis as early as 10 days after implantation in 90 % of host mice. These cells expressed elevated levels of genes whose products promote invasion, migration, and mobilization of bone marrow derived cells (BMDCs). Mice bearing tumors from CT26-FL3 had elevated serum levels of OPN, MMP9, S100A8, S100A9, SAA3, and VEGFA that promote invasion and BMDC mobilization, and showed enhanced BMDC recruitment to the liver where they established a pre-metastatic niche. This model provides an important platform to characterize metastatic cells and elucidate tumor-host interactions and mechanisms that drive liver metastasis of CRC.

Combination therapy of gemcitabine or oral S-1 with the anti-VEGF monoclonal antibody bevacizumab for pancreatic neuroendocrine carcinoma

We previously reported that the administration of bevacizumab for pancreatic neuroendocrine tumors inhibited angiogenesis in the host, resulting in tumor growth inhibition. In light of these results, we compared the effect of bevacizumab/gemcitabine/S-1 combination therapy vs. bevacizumab monotherapy. The QGP-1 pancreatic neuroendocrine carcinoma cell line and the BxPC-3 ductal cell carcinoma cell line were transplanted into the subcutaneous tissue of mice, and the mice were treated for 3 weeks with bevacizumab [50 mg/kg intraperitoneally (i.p.) twice weekly], gemcitabine (240 mg/kg i.p. once weekly) and S-1 (10 mg/kg orally five times weekly). The antitumor effect and side effects were evaluated by measuring the tumor volume and weight and by changes in body weight, respectively. The tumor volume became smaller (from the maximum volume) in the group treated with bevacizumab, gemcitabine and S-1 (BGS) and the group treated with bevacizumab and gemcitabine (BG). A significant difference was noted in the tumor weight between the BG group and the group treated with bevacizumab alone. A relatively significant decrease in the body weight was observed in the BGS and BG groups. We conclude that gemcitabine is appropriate as a drug used in combination with bevacizumab for pancreatic neuroendocrine tumors.